Microphone.



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MICROPHONE.

Application filed saw. 21, 1897.)

(No Model.)

Inventor.

VVL'ZTw 5 e 5 .7 FFIQQ JULIUS OTTO ZWARG, OF FREIBERG, GERMANY.

MICROPHONE.

SPECIFICATION forming part of Letters Patent No. 641,425, dated January16, 1900.

Application filed September 21, 1897. Serial No- 662,504. (No model.)

T0 to whom it may concern:

Be it known that I, JULIUS OTTO ZwARe, a subject of the King of Saxony,residing in Freiberg, Saxony, Germany, have invented certain new anduseful Improvements in Microphones, of which the following is a specification.

This invention relates to a microphone with granulated carbon carryingcontact holes which are inclined toward the diaphragm of the front faceof the chamber holding the granulated carbon,an opening being providedfor the filling of said chamber.

The accompanying drawings show this microphone.

Figure 1 is a transverse vertical section of the invention, and Fig. 2is a section on the line at y of Fig. l.

The granulated carbon g is laid into a removable metallic box a, therear face Z? of which is provided with an opening for the filling, theother face a, which is composed of a disk thicker at the bottom than atthe top, having numerous perforations (1 no matter what may be theirsection, forming a large surface of contact between the granulatedcarbon, the wall a, and the diaphragm p, which is fastened between thebox a and the plate 6, serving to fix the apparatus. The plate e isprovided at its center with a screwthreaded opening receiving themouthpiece c. All the perforations C02 are inclined downward toward thediaphragm. The efiect of this inclination is to render slower by thissimple device the motion toward the back opposite the diaphragm of thegranulated carbon that may go into them, since this carbon settles atthe lower part of the perforated side. As is well known, the greatnumber of holes increases the contact-surface and decreases consequentlythe resistance to the electric current between the carbon and thediaphragm, so that the electric current for the call-bell may go throughit easily. The plate 6, with the mouthpiece c, is electrically insulatedfrom the envelop by means of a nonconducting diaphragm c and ofinsulated setscrews f. Its duty is to connect one of the ends of theelectric circuit, whereas the other end is in connection with the upperpart of the box a through the screw 01. This screw 61 also serves toshut the filling-opening of the box a.

What characterizes this microphone is its great simplicity, for it iscomposed of but a few pieces of metal. Besides this, the appa ratus isself-regulating on account of the inclined perforations a intended tofacilitate the falling of the granulated carbon against the diaphragm.Finally, as the filling of carbon can be very easily regulated by meansof the filling-hole any workman or other person may be trusted to takecare of the apparatus and regulate it.

Having fully described my invention, what I claim, and desire to secureby Letters Patent, is-

1. In a microphone the combination of a box open at the front containinggranular car bon, a plate closing the front of said box and providedwith a central hole for the mouth piece, a back plate I) provided with afeedopening for granulated carbon opposite the thickest part of thecarbon mass, a diaphragm clamped between said front plate and box and adisk against said diaphragm provided with numerous holes or passagesfrom back to front, the mass of carbon contained within the said boxbeing arranged to communicate with the said holes and supply the sameand being also of downwardly-tapering form as to thickness,substantially as set forth.

2. In a microphone the combination of a .box open at the frontcontaining granular carbon, a plate closing the front of said box andprovided with a central hole for the mouthpiece, a diaphragm clampedbetween said plate and box and a disk against said diaphragm providedwith tubular holes from back to front inclined downward, said diaphragmincreasing in thickness from top to bottom, substantially as set forth.

3. In a microphone the combination of a box containing granular carbonprovided with a feed-opening near its periphery at the point normallyheld uppermost, and a screw adapted to close said opening and to act asan electric conductor, substantially as set forth.

4. In a microphone, the combination of a the upper part of thedownwardly-tapering diaphragm and mouthpiece witha perforated space leftby said disk and with means for disk in contact with the said diaphragmand closing the same, substantially as set forth.

having its rear face inclined downward and JULIUS OTTO ZWARG. 5 rearwardand abox containing the carbon and Witnesses:

the said perforated disk, the said box being HERNANDO DE SOTO,

provided with a feed-opening which supplies PAUL ARRAS.

